Electronic surgical metal body locator



C 4 Sheets-Sheet l Jan. 29, 1946. D. M. SPEAKER ELECTRONIC SURGICALlMETAL BODY LOCATOR Filed June 16, 1944 H. y QM A BY Q f l ATTORNY? Jan.29, 1946. D. M. SPEAKER ELECTRONIC SURGICAL METAL, BODY LOCATOR i.

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UNITED STATES PATENT OFFICE ELECTRONIC SURGICAL METAL BODY LGCATOR DavidM. Speaker, East Orange, N. J.

Application June 16, 1944, Serial No. 540,733

(Cl. 128-L5) 12 Claims.

This application relates to a device for locating foreign metal bodiesin living tissue. More specifically it relates to a surgical metal bodylo'- cator adapted to serve, alone, or as an adjunct and mixer shown inthe previous figures is substituted for the said separate crystaloscillator to known X-ray and uoroscope means, for loand mixer. V catingmetal bodies in living tissue'.A In the embodiment of the inventionindicated An object of the invention is to provide-av in Figure 1 asource of stable high frequency simple, practical and eiiicient locatorof the above oscillations such for example as crystal oscillatormentioned kind. A, which may be a tube of the 6V6 type, and a 4Anotherobject of the invention is to provide l0 negative transconductance typeof oscillator, such a metal body locator for surgical use, which willfor example as transitron oscillator B (see The have high sensitivity tonon-ferromagnetic as Radio Engineering Handbook, McGraw Hill well as toferromagnetic metal. Book Co., Inc. 1941, 3rd Edition, page 302, andlAnother object of the invention is to provide Ultra-High-FrequencyTechniques, D. Van

such a. device which will have high accuracy of l5 Nostrand Co., Inc.,1942, pages 192, 193,-and 194), localization. which may be a tube of the6A8 type, are shown Another objectof 'the invention is to provideconnected to a mixer tube C, which may be of a device of the kinddescribed which is adapted the 6SA7 type. As will be explained, thetransito indicate to the operator in a clear and definite tronvoscillator B includes a parallel tuned circuit -manner the position of aforeign metal body with I0 -the coil II of which is contained within aturespect to a probe forming part of the device. bular envelope/or'probe I2, which is moved over- Another object of the invention is toprovide the patients body, and into any incision made a metal bodylocator wherein small changes in to locate the exact positionof aforeign metal the fundamental frequency will produce relatively body,such as a. bullet, piece of shrapnel, or a, fraggreat changes in thefrequency of a harmonic ment of a needle, or the like. The mixer tubethereof. l C is in turn connected to a frequency indicating Otherobjects of the invention will be in part device adapted to inform theoperator of changes obvious or in part pointed out hereinafter. in beatfrequency which occur in the output of The invention accordinglyconsists in the feathe mixer tube due to changes in the harmonic 'turesof construction, combinations of elements, 30 frequency of thetransitron oscillator B resulting arrangements of parts, and in theseveral steps from changes in the inductance of the tuned cirandrelation andorder of each of said steps to cuit I0 depending on theproximity of the said one or more of the others thereof, all as will beprobe to the metal foreign body. The frequency pointed out in thefollowing description, and the indicating device may be adapted to giveaudiy scope of the application of which will be inditory or visualsignals to the operator as desired, cated in the following claims. andmay be for example a set of ear-phones I3a,

'I'he invention will best be understood if the a loud speaker I3, or avisual signal device |3b. following description is read in connectionwith Preferably the frequency indicating device is conthe drawings, inwhich: nected to the mixer tube C through an amplifier Figure 1 is aview of a circuit representing one 40 Il. As oscillators and mixingtubes of the type embodiment of my device; referred to are ywell knownand no claim is made Figure 2 shows the circuit of Figure 1 modified tothem per se they are not individually described by the insertion of aharmonic amplifier between in detail herein but, only as parts of thecircuits B and C; y disclosed and claimed herein.

Figure 3 shows another modification of the cir- *45 The frequency ofoscillator A may desirably be cuit of Figure 1 in which a multi-vibratoris inn the three to four megacycle range. vThe alterserted between B andC; nating voltage generated at this frequency in the Figure 4 is a fullyschematic representation of secondary winding of the tank coil I5 issupplied a circuit similar to that shown in Figure 1 .but to the grid I6of the mixer tube C. The high showing an amplifier tube added to-thecircuit of frequency signals of oscillator A are mixed in Figure 1between B and E; the mixer tube C with the frequency of the nega- Figure5 is a view similar to Figure 4 but showtive transconductance typeoscillator B which is ing amplifying means insertedbetween E and C;supplied to grid II of the mixer tube C. v'The and fundamental frequencyof oscillator B is deter- Figure 6 is a .view of a modification ofcircuits 55 mined by the parallel tuned kcircuit I0, and is somewhatabove the audio range, being of the order of 25 kc. to 40 kc. The waveshape in the plate circuit of oscillator B (across I8) isdistorted-intentionally (through choice of component values). Theharmonic component selected is mixed, as previously described, with thereference high frequency signal from oscillator A. A small change in thefundamental frequency of oscillator B will produce a relatively greatchange in the harmonic,` and this change will be equal t the changeproduced in the fundamental multiplied by the ratio of the frequency ofthe harmonic to that of the fundamental. In this way the apparatus ismade sensitive to small changes Abrought near metala perceptible andunmistak-v able variation in the beat note will occur. If the If a loudspeaker I 3 or head receiver set Ia are used as the frequency indicatingdevice, the

' change in the frequency of the audible tone is metal isferromagneticits proximity will increase the inductance of coil II andhence raise the fundamental frequency of oscillator B. If the metal isnot ferromagnetic the eddy current losses induced in it will behave as areflected resistance in the tuned circuit i0 and thus Vary the.fund amental frequency. This variation of the fundamental due to a smallmetallic object is small in magnitude, but the frequency shift ismagnified through utilization of the harmonic as explained above.

The ratio of capacity to inductance in the tuned circuit I0 is ratherhigh. The tuning capacity is made relativelylarge so that the effects ofthe capacity between the tissues being explored with the probe and theprobe coil i I will not in themselves seriously affect the fundamentalfrequency of oscillator B. Tuning condenser Ila may include a small airtrimmer (not shown) condenser with which these effects may be balancedif desired.,

Preferably the coil II is so woundthat the ground end represents theAend of the winding (outside) A certain amount of shielding is auto-Vmatically achieved in this way.

Between the mixer tube C and the amplifier I4 a low pass filtercomprising resistance I9 and condenser 20, is preferably provided toremove rate of change in frequency decreases. After relatively littleexperience with the device the operator is able to estimate veryaccurately the distance between the probe and the metal body.

particularly if the approximate size of the metal body is known throughprior X-ray studies, the

sensitivity of the circuit being somewhat higher for large than forsmall particles.

If desired the tuned circuit I0 may contain a plurality of coils II,which may be of different size and may be individually enclosed inprobes of different size so that a larger probe may first be used tolocate the general position of the foreign metal body, after which asmaller probe may be employed to locate the metal body with greaterprecision. A probe I2 may conveniently be made of Lucite or a likematerial adapted to conduct light from a source provided in the han- Asthe probe is moved away from the metal body the solidated in the singletube F.

easily detected. and similarly 1r a visual indicator I3b is employed themovements thereof are amput of oscillator B may be amplified before itisy supplied to the mixer tube C thereby decreasing the amount to whichthe output of the mixer tube need be amplified. The harmonic amplifiermay be a tube of the 6SJ7 type and is not described in detail hereinsince it is well known.

In Figure 3"a further modication is shown in which a multi-vibrator E isconnected between the transitron oscillator B and the mixer tube C. Inthe circuit of Figure 2 the harmonic ampliner D serves' to amplify theharmonic of the transitron oscillator which is directly mixed with thehigh frequency signal supplied by the crystal oscillator A. In thecircuit of Figure 3, however, the harmonic frequency which is mixed withthe high frequency signal of oscillator A is supplied by themulti-vibrator E, and the transitron oscillator B, instead of providingthe harmonic frequency, is utilized to stabilize the frequency of themulti-vibrator E. The multi-vibrator E is so designed as to -oscillateat a. frequency correspending to a multiple of the oscillator B, and maybe a tube of the 6SN7 GT type. The harmonic of the multi-vibrator E ismixed with the signal from oscillator A. Without the multi-vibrator avery high order of harmonic of oscillator B would be required. Byoperating the multivibrator so that its fundamentalfrequency isamultiple of the fundamental frequency of oscillator B a multi-vibratorharmonic, of consider-l If desired an amplifier tube 2I may be employedbetween oscillator B and the multi-vibrator E (so-called buffer stage)in the circuit of Figure 3 (see Figure 4) to isolate B from E andthereblr preventundesired interaction. Similarly a har monic amplier 22may be employed if desired between the multi-vibrator E and the mixertube C (see Figure 5), to both increase the amplitude of the desiredharmonic and-to tend to suppress undesiredfrequency components.otherwise transmitted to mixer tube C.

In Figure 6 I have shown another embodiment of my invention in which thefunctions of the crystal oscillator A and the mixer C `are con- Thissubstitution may be made in the circuit of any of the circuits ofFigures 1 to 5 inclusive. For combining the functions of a crystaloscillator and a mixer in a single tube I employ any known type of tube.such for example as a 6K8 type, which is known as a. frequency converteror conventionally a converten Since tubes of the 6K8 type are well knownI will not describe it in detail herein. as no claim is made to suchtube per se. The

frequency converter tube F illustrated herein circuits `associated withgrids 21 and 29 respectively. Interconnected grids 2| and 21 areconnected with crystal oscillator 3| which is conaaosm'r f netted withplate z5 through the tuned circuit connected with a multi-vibrator whichin turn may be connected with a negative transconductance type ofoscillator as shown in any one of Figu'es 3, 4, and 5 inclusive. Ifthe'. source of harmonic frequency is supplied through a har-l monicamplifier, as shown in Figure 2, the circuit will include a tunedcircuit. If the connection from the source of harmonic frequency doesnot include a harmonic amplifier the tuned circuit may be providedintermediate the source o f harmonic frequency and grid 28 to select theparticular harmonic desired and to reject unwanted frequencies. Y

The output .beat frequency signal from plate 2B of combined crystaloscillator and mixerF is -coupled,qthrough plate resistor 33 and platecoupling condenser 34, with amplifier I4 which is in turn connected witha frequency indicating device i3.

It will be understood that by my invention, various modifications ofwhich are described above, a surgical metal body locator is providedwhich has high sensitivity to non-magnetic as well as to magneticmetals; which has high accuracyof localization and is characterized bythe fact that as the probe is moved so thatits longitudinal axis isplaced in line with the objects to be detected, a very perceptablechange in audio tone (or visual signal) is noted; and which is adaptedto give the operator`a dependable indication of the distance of themetal body lfrom the probe.

It will thus be seen that there has been provided by this invention amethod, apparatus, andan article in which the various objectshereinabove set forth together with many thoroughly practical advantagesare successfullyv achieved. As various possible embodiments might bemade of the mechanical features of the above invention and asthe artherein described might be varied in various. parts, all withoutdeparting from the scope of the invention, it is to be understood thatall matter hereinbefore set forth or shown in the accompanying drawingsis'to be interpreted as illustrative and not in a limiting sense. f v

What I claim is: I

1. The method of locatingan invivo foreign vmetal body which comprisesmixing a high har-l monic of a stable source of electrical oscillationswith a high frequency signal from another source of electricaloscillations .so as to produce a beat note in the audio range,connecting to said first to obtain increased beat frequency variatlonofthe indicator response. Y

2. The method of locating a foreign metallic body in living tissue whichcomprises mixing a,

harmonic produced by a stable source of electrical oscillations somewhatabove the audio range with a high frequency signal from another sourceof electrical oscillations well beyond the audio range, and therebyproducing a beat note. in the audio range, controlling the fundamentalfrequency of said first mentioned source of oscillations by means of atunedcircuit connected in parallel therewith and including a movablecoil, in .zerposing a harmonic amplier between said first source ofoscillations and the said mixing step thereby amplifying the harmonic ofthe output of the said first source of oscillations, and utilizing thesaid beat note resulting from said mixing step to actuate a frequencyindicatonand moving said coil in a direction to obtain increased beatfrequency variation of the indicator response.

3. The method of locating a metal foreign body .in living tissue whichcomprises mixing a harmonic of a frequency produced by a multi-vibratorwith a high frequency signal, controllingthe frequency of themulti-vibrator by connecting it 4. An electronic surgical metal bodylocator comprising a tuned circuit, means for probing having therein acoil connected in said tuned circuit, an oscillator of the negativetransconductance type connected to said tuned circuit, andoscillatormeans adapted to produce a high fre.- quency signal, means for mixingthe .frequencies of said oscillations to produce an output beatfrequency signal, a frequency indicating device, and

an amplifier between said mixing means and said signalling device.

5. An electronic surgical metal body locator comprising, a mixer tubehaving a grid connected to a crystal oscillator, and having another gridconnected to a transitron oscillator through a vharmonic amplifier, afrequency indicating device connected to said mixer tube through anamplifier, and a tuned circuit connected to said transitron oscillatorand including a coil enclosed vin a tubular envelope permitting it to bemovedv and to vthereby modify the. frequency of said transitronoscillator according to changes in impedance of said tuned circuitdepending on the position of said tubular enveloperelative to said metalbody.

comprising an electrical circuit including, a. mixer tube having a gridconnected to a crystal oscilmentioned source of oscillations a tunedcircuit including a coil located in a movable probe, connecting saidmixing means to a. frequency indilator, and having another gridconnected to -a multi-vibrator 'which is in turn connected to a`transitron oscillator, said multi-vibrator being so designed las tooscillate at a frequency corresponding to a multiple of the Afundamentalof said transitron oscillator, a tuned circuit conlnectedto saidtransitron oscillator including a coil contained in a tubular envelope,a device 6. An electronic surgical metal body locator tube, connectedbetween a crystal oscillator, and,

a multi-vibrator which is in turn connected to a transitron oscillator,said multi-vibrator being so designed as to oscillate at a frequencycorrespondingto a multiple of ythe fundamental of said transitronoscillator,v a tuned circuit, connected to s aid transitron oscillator`and including a coil contained in a tubular envelope, a'device forindicating changes in frequency, and amplifier means between saidtransitron oscillator and said multi-vibrator.

8. An electronic surgical metal body locatoi` comprising an electricalcircuit including, a mixer tube connected between a crystal oscillator,and

a'multi-vibrator which is in tum connected to a transitron oscillator,said multi-vibrator being so designed as to oscillate at a frequencycorresponding to a multiple of the fundamental of saidtransitronoscillator, a tuned circuit connected to said transitron oscillatorincluding a coil contained in atubular envelope, a device for indicatingchanges in frequency, connected to said mixer tube and a harmonicamplifier between said multi-vibrator and said mixer tube.

9. An electronic surgical metal body locator comprising a tuned circuitincluding a coil,-at least the said coil of said tuned circuit beingenclosed in a tubular envelope, said tuned circuit being connected inparallel, by a flexible.

conductor, with a stable sourceof oscillations the fundamental frequencyof which is determined by said parallel tuned circuit, a constant highfrequency source, means for mixing the output of the harmonic of saidfundamental frequency source with the output of said constant highfrequency source, and means for indicating changes in the frequency ofthe output of said mixing means.

10. In combination with an electrical circuit for locating foreignmetalbodies in living tissue which includes a multi-vibrator and acrystal oscillator connected through the medium of a mixer tube, the useof a negative transconductance type of oscillator to provide a stablereference frequency for the output of said multivibrator. 'v

11. In combination in an electrical circuit for locating foreign metalbodies in living tissue which includes a plurality of sources ofoscillations and means for mixing the frequencies of said oscillationsto produce an audible beat note, the use of a negative transconductancetype of oscillator to provide a harmonic component to be mixed with thefrequency of said other oscillator, whereby a small change in thefundamental frequency of said negative transconductance type yoscillatorwill produce a relatively great change in the frequency of the harmonicmixed with the frequency 'of said other oscillator.

12. An electronic surgical metal body locator comprising, a crystaloscillator, and a negative transconductance oscillator, both feedinginto a mixer stage, and a, high frequency indicator, the electronic.tube elements of the crystal oscillator and the electronic tube elementsof the' mixer being enclosed in a single envelope, said high frequencyindicator being connected to the plateA included in the said electronictube elements of the mixer to indicate the" frequency of the output beatsignal resulting from the mixing of the frequency of said crystaloscillator with the harmonic of said negative transconductanceoscillator.

DAVID M. SPEAKER.

